The applicant of the present application has proposed a vibration damping material composed mainly of a composition prepared by the following method as a vibration damping material having excellent heat resistance and vibration-damping properties (see, for example, Patent Literature 1). Specifically, at least one monomer selected from alkyl acrylate, alkoxyalkyl acrylate, alkyl methacrylate, and alkoxyalkyl methacrylate is polymerized with a monomer that serves as an epoxy-based crosslinking point. 100 parts by weight of acrylic rubber having a molecular structure formed by the polymerization is mixed with, in an external ratio, 0.01 to 15 parts by weight of organic peroxide that crosslinks the epoxy-based crosslinking points with each other, 1 to one hundred parts by weight of tackifying resin, and 1 to 20 parts by weight of a plasticizer. Further, the composition is formed by crosslinking between the crosslinking points of the acrylic rubber with each other through the organic peroxide.
Since the vibration damping material described in Patent Document 1 is a vibration damping material that exhibits a loss coefficient (tan δ) of one or more that is different from the conventional acrylic rubber-based vibration damping material, the effect of exerting excellent vibration-damping properties equivalent to or superior to that in the butyl rubber-based vibration damping material can be attained.
Further, unlike the conventional butyl rubber-based vibration damping material, the vibration damping material has a low compression permanent strain even under temperatures above 100° C. and therefore exerts an effect of having heat resistance superior to that of the butyl rubber-based vibration damping material. Hence, the vibration damping material can be utilized in environments that are likely to be high temperature, for example, in an engine room of automobiles or the like.
In addition, the vibration damping material is manufactured at a lower cost than silicone rubber, fluoro-rubber, or the like and therefore exerts an effect that a final product can be provided at low price. Further, unlike silicone rubber, the vibration damping material is not a cause of electric contact fault such as a rise in contact resistance or a contact defect and therefore provides an effect that the vibration damping material can be used in electrical apparatuses and electronic apparatuses.